Growth Percentage

Hi, I was hoping someone can help me solve this conundrum. I have a chart of crude steel production per month and which also shows production growth. I would really like to know how this growth percentage has been calculated.Crude Steel Prod.jpg
Rgds
Mike

Not sure exactly what your question is. If you are asking about the "Poly. (Global Production Growth)" , It is tough to tell exactly from your screen shot, but I would speculate that the "Poly. (Global Production Growth)" was created as a trendline to the "Global Production Growth" line as "polynomial". It appears to be a polyol of order 2, so it would have used the raw X,Y data points to create an equation of the form:
y= A0 + A1x + A2x²

Internally the program uses a linear regression method to find the values of A0,A1, and A2 so that the resulting equation minimizes the square of the deviation from the observed Y value at each X to the calc Y at that X. The methodology typically involves matrix math [see for example http://en.wikipedia.org/wiki/Regression_analysis]

Hi Steve, thanks for your reply. You must be Steve Austin because that answer is coming from a bionic brain and you answered my next question before i asked it.
I managed to finally figure out that the growth line is calculated on a y-o-y basis, rather than a mth-o-mth basis, and then your answer helps solve the rest.
Many thanks
Mike